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Bring Back 1962-63

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  1. ARCTIC AMPLIFICATION I just produced a comprehensive update on the Arctic thread - here's the link: https://www.33andrain.com/topic/1367-the-arctic-thread/?do=findComment&comment=131043 This shows the current ice extent, 2m surface temps, SSTs and snow cover up there. Mixed news! There have been a number of comments on this and other threads as well as in our PM thread wrt to Arctic Amplification and whether it's partly responsible for interfering with some of the impacts that we might usually associate with the teleconnections and in response to a major SSW and periods of strong tropical forcing. Since last summer we have seen the El Nino struggling to establish itself with problems related to ocean/atmosphere coupling. Then this winter we have seen similar problems with troposphere/stratosphere coupling. There are now some more positive indications that HLB may start to prevail with another delayed Spring and generally colder conditions dominating for the the second half of February and well into March. We can monitor current developments in line with the teleconnections on this thread. Once this winter and any SSW impacts are over we can go through many of the factors that have confounded the experts, the pros, the specialists and longer range forecasters. While we can examine the teleconnections on here, I also plan to take one aspect of it , "Arctic Amplification" and encourage some specialist posts on the Arctic thread. Just to whet a few appetites, I'll refer to several papers that Malcolm (@Blessed Weather) and I placed into the research portal this week. The first two are very recent papers (published in January 2019) - one dealing with SSW down welling issues and the other on impacts of the QBO on the N hem winter circulation. I do not have time to review these papers now. The Corresponding Tropospheric Environments during Downward-extending and Non-downward-extending Events of Stratospheric Northern Annular Mode Anomalies Observed and Simulated Teleconnections Between the Stratospheric Quasi‐Biennial Oscillation and Northern Hemisphere Winter Atmospheric Circulation The next two papers are directly related to Arctic Amplification. The first one is an excellent paper by Judah Cohen - I'll leave that to Malcolm to review that one - he may wait until the winter is over and the "AA" debate begins. I shall review the second paper briefly now. An observational analysis: Tropical relative to Arctic influence on mid-latitude weather in the era of Arctic amplification The urgency of Arctic change This climate change paper was published in "ScienceDirect" last November and was jointly produced by a number of leading scientists from various organisations. I am always wary of any misrepresented facts and claims on this subject but this one is a balanced paper, albeit with some worrying conclusions. Part of it is completely relevant in terms of how Arctic Amplification and ice loss are already impacting on global atmospheric patterns. Here's the abstract: This article provides a synthesis of the latest observational trends and projections for the future of the Arctic. First, the Arctic is already changing rapidly as a result of climate change. Contemporary warm Arctic temperatures and large sea ice deficits (75% volume loss) demonstrate climate states outside of previous experience. Modeled changes of the Arctic cryosphere demonstrate that even limiting global temperature increases to near 2 °C will leave the Arctic a much different environment by mid-century with less snow and sea ice, melted permafrost, altered ecosystems, and a projected annual mean Arctic temperature increase of +4 °C. Second, even under ambitious emission reduction scenarios, high-latitude land ice melt, including Greenland, are foreseen to continue due to internal lags, leading to accelerating global sea level rise throughout the century. Third, future Arctic changes may in turn impact lower latitudes through tundra greenhouse gas release and shifts in ocean and atmospheric circulation. Arctic-specific radiative and heat storage feedbacks may become an obstacle to achieving a stabilized global climate. In light of these trends, the precautionary principle calls for early adaptation and mitigation actions. The part that interests me is contained in these two sections (quoted in full below): 4.1. Patterns of atmospheric circulation Shifts in Arctic sea ice and snow cover and increased surface temperatures are warming the lower atmosphere in the Arctic, which decreases air density and north-south horizontal pressure gradients and thus influences wind patterns and the jet stream. There is evidence for regional Arctic/midlatitude weather connections from Barents-Kara sea ice loss and cold air outbreaks into eastern Asia (Wu et al., 2011; Kim et al., 2014; Kretschmer et al., 2016). Although there have been extensive new sea-ice-free areas in all years of the past decade, latitude and longitudinal phasing of the tropospheric jet stream pattern have not been conducive for North American midlatitude weather linkages in most years (Kug et al., 2015; Ayarzagüena and Screen, 2016; Ballinger et al., 2017; Chen and Luo, 2017; Cvijanovic et al., 2017; Overland and Wang, 2018), indicating the importance of internal variability and other forcings such as midlatitude and equatorial sea surface temperatures. Despite a growing literature (Cohen et al., 2018; Vavrus, 2018), there is little consensus on the topic in the scientific community (Wallace et al., 2014; Barnes and Screen, 2015; McCusker et al., 2016). At present what we can say is that global forcing from the Arctic (sea ice loss, increased temperatures, and moisture) will continue to increase. There is case study evidence that multiple linkage mechanisms are regional, episodic, and based on amplification of existing jet stream wave patterns (Overland et al., 2014; Cohen et al., 2018). 4.2. Atlantic Ocean circulation There is a hypothesis for future impact of Arctic change on ocean circulation in the North Atlantic due to the accumulation of freshwater in the Arctic (Prowse et al., 2015; Carmack et al., 2016; Marnela et al., 2016; Rudels, 2016; Yang et al., 2016). There is paleoclimate data that show large changes to Atlantic Ocean circulation patterns. This topic is controversial as some current literature suggests weakening of Atlantic meridional overturning circulation (AMOC) related to Arctic warming (Sévellec et al., 2017), while other work shows that the Arctic component of AMOC did not weaken during the last two decades of Arctic change (Jochumsen et al., 2017). Rather than react to this paper's climate change statements and possible predictions for the middle of this century and beyond, I feel that we should focus on the impacts that we have already seen and how and to what extent these are influencing, dominating or over riding some of the key teleconnections. We have a number of other papers already in the portal under the Arctic Amplification heading and we have many more to add. Some of these are factual and uncontroversial. I hope that when we get the debate going that we can discuss these and other related facts and, to a certain extent, put our personal opinions to one side to enable us to make a balanced assessment. More on this in a few weeks time. David
  2. Bring Back 1962-63

    The Arctic Thread

    GENERAL ARCTIC UPDATE I had been hoping to spend more time on this thread but I have had various business commitments which have reduced my overall weather time and only some of this can be here on the Arctic thread. I was hoping that a few more members would get involved on this thread. During the Spring, I intend to start a debate on here wrt to Arctic Amplification and the extent of its influence on both the tropospheric and stratospheric patterns. I have a number of key papers to review on this fascinating and highly important subject. In the meantime, this post will provide a long overdue update on current Arctic ice extent, surface temperatures, SSTs and snow cover. I do not have time to produce a long report but I'll make brief comments below each chart. Please note that some of the regular charts are not available at the time of this report (for various reasons, including the past shutdown access problems) but I found acceptable substitutes. Current ice extent is running well below the 1981-2010 30 year mean (more later). The large beige area (which includes the area around the pole that is not showing up properly on this chart) has the thickest ice - over 50 cms. 2018-19 ice extent is running well below quartile mean and slightly below the decadal mean (more later). It is currently around the 4th lowest on record for early February. This charts shows the ice extent for each January since the start of the satellite recording era in 1979. 2019 is well above the last 2 Januarys. Just above 2004, slightly below the current decadal average and well below the 1980s, 1990s and 2000s decadal means. This chart is from the excellent Zach Labe website (all links are shown in my introductory post to this thread). Zach is expanding his site steadily and it's well worth a visit. Arctic surface temps have been generally lower than in the last few years (more below). In fact January 2019 finished well below the 30 year mean with overall Arctic Ocean 2m surface temps nearly 1c below and the whole Arctic region (north of 66N) just over 1c below. This month to date sees the region continuing over 1c below the 30 year mean, although the ocean 2m temps are only slightly below the mean. In fact January 2019 is ranked the 17th coldest out of all 40 Januarys and the coldest since 2004 in stark contrast to some recent years. It is easy to see why the ice extent is struggling to expand despite the below average 2m temps. The white area is the ice sheet and the SSTs quickly rise to 3c to 5c just beyond it. Nevertheless, should the temps continue to be near to or below the 30 year mean, then further reasonable ice expansion is probable during February and into March. Further good news is that the SST anomalies in the open waters are generally running at 1c to 3c above the "1971-2000" 30 year mean (which would be even closer to the 1981-2010 mean - not used by ClimateReanalyzer). The last 3 winters saw wide areas over 4c above the mean and some spots nearer 6c to 8c above. So, 2018/19 SST anomalies are trending down from their extremely high levels - a long term legacy from the 2015 super El Nino. The full access to the NOAA snow data is not available but I obtained this N Hem comparison chart. Snow cover is currently running at a similar level to this time last year and around the longer term mean. Slightly below in CONUS and very slightly above in central Asia. The snow extent increased markedly through March 2018 to substantially above average following the SSW impacts then. Will we see a repeat this year? Overall, it is mixed news but with lower 2m surface temps persisting, we may see a late winter ice extent recovery. I'll finish by quoting part of the latest NSIDC monthly report which was published this Tuesday and the comments relate to the position on 31st January 2019: In January 2019, a pattern of high-altitude winds in the Arctic, better known as the polar vortex, weakened, sweeping frigid air over North America and Europe in the second half of the month. Arctic sea ice extent remained well below average, but temperatures in the far north were closer to average than in past years. Arctic sea ice extent for January averaged 13.56 million square kilometers (5.24 million square miles). This was 860,000 square kilometers (332,000 square miles) below the 1981 to 2010 long-term average sea ice extent, and 500,000 square kilometers (193,000 square miles) above the record low for the month set in January 2018. January 2019 was the sixth lowest January extent in the 1979 to 2019 satellite record. The average rate of daily ice growth of 51,200 square kilometers (19,800 square miles) was faster than the long-term average. Ice growth primarily occurred in the Bering Sea and Sea of Okhotsk in the Pacific sector as well as in the Labrador and Kara Seas. Some ice spread to the northeast of Svalbard, while retreating slightly to the northwest of these islands. Total ice extent was tracking at eighth lowest on January 31, with below average extent in nearly all sectors of the Arctic. Here's the link to the full report and a load more data: https://nsidc.org/arcticseaicenews/ I'll produce another update next month. David
  3. The urgency of Arctic change Authors: James Overland, Edward Dunlea, Jason E.Box, Robert Corell, Martin Forsius, Vladimir Kattsov, Morten Skovg ård Olsen, Janet Pawlak, Lars-OttoReiersen and MuyinWang Published: November 27th, 2018 Abstract: This article provides a synthesis of the latest observational trends and projections for the future of the Arctic. First, the Arctic is already changing rapidly as a result of climate change. Contemporary warm Arctic temperatures and large sea ice deficits (75% volume loss) demonstrate climate states outside of previous experience. Modeled changes of the Arctic cryosphere demonstrate that even limiting global temperature increases to near 2 °C will leave the Arctic a much different environment by mid-century with less snow and sea ice, melted permafrost, altered ecosystems, and a projected annual mean Arctic temperature increase of +4 °C. Second, even under ambitious emission reduction scenarios, high-latitude land ice melt, including Greenland, are foreseen to continue due to internal lags, leading to accelerating global sea level rise throughout the century. Third, future Arctic changes may in turn impact lower latitudes through tundra greenhouse gas release and shifts in ocean and atmospheric circulation. Arctic-specific radiative and heat storage feedbacks may become an obstacle to achieving a stabilized global climate. In light of these trends, the precautionary principle calls for early adaptation and mitigation actions. Link to full paper (on the "ScienceDirect" website): https://www.sciencedirect.com/science/article/pii/S1873965218301543?via%3Dihub Link to pdf early manuscript version of the paper: https://ac.els-cdn.com/S1873965218301543/1-s2.0-S1873965218301543-main.pdf?_tid=9ec55a0a-269b-4468-a4cc-531cf64a8ce5&acdnat=1549639446_79edbe550be051725ffca5149afc40c3
  4. The Corresponding Tropospheric Environments during Downward-extending and Non-downward-extending Events of Stratospheric Northern Annular Mode Anomalies Authors: Zhang, Wenshou Tian, Jiankai Zhang, Jinlong Huang, Fei Xie and Mian Xu Published: 25th January, 2019 Abstract: Using the NCEP/NCAR reanalysis dataset, this study classifies stratospheric Northern Annular Mode (NAM) anomalies during negative/positive phase into two categories—anomalies extending into the troposphere (referred as negative/positive TEs) and those not extending into the troposphere (referred as negative/positive NTEs), and the corresponding tropospheric environments during the TEs and NTEs are identified. Compared with that for the negative NTEs, the upward wave fluxes entering the stratosphere are stronger and more persistent during the negative TEs. Furthermore, the stronger and more persistent upward wave fluxes during the negative TEs are due to more favorable conditions for upward wave propagation, which is manifested by fewer occurrences of negative refractive index squared in the mid-high latitude troposphere and stronger wave intensity in the mid-high latitude troposphere. However, the tropospheric wave intensity plays a more important role than the tropospheric conditions of planetary wave-propagation in modulating the upward wave fluxes into the stratosphere. Stronger and more persistent upward wave fluxes in the negative TEs, particularly wave-1 fluxes, are closely related to the negative geopotential height anomalies over the North Pacific and positive geopotential height anomalies over the Euro-Atlantic sectors. These negative/positive geopotential height anomalies over the North Pacific/Euro-Atlantic are related to the positive/negative diabatic heating anomalies and the decreased/increased blocking activities in the mid-high latitudes. The subtropical diabatic heating could also impact on the strength of the mid-high latitude geopotential height anomalies through modulating horizontal wave fluxes. For positive NAM events, the results are roughly similar to those for negative NAM events, but with opposite signal. Link to full paper: https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-18-0574.1 https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2018JD029368
  5. Observed and Simulated Teleconnections Between the Stratospheric Quasi‐Biennial Oscillation and Northern Hemisphere Winter Atmospheric Circulation Authors: Martin B. Andrews , Jeff R. Knight, Adam A. Scaife, Yixiong Lu, Tongwen Wu, Lesley J. Gray and Verena Schenzinger Published: 15th January, 2019 Abstract: The Quasi‐Biennial Oscillation (QBO) is the dominant mode of interannual variability in the tropical stratosphere, with easterly and westerly zonal wind regimes alternating over a period of about 28 months. It appears to influence the Northern Hemisphere winter stratospheric polar vortex and atmospheric circulation near the Earth's surface. However, the short observational record makes unequivocal identification of these surface connections challenging. To overcome this, we use a multicentury control simulation of a climate model with a realistic, spontaneously generated QBO to examine teleconnections with extratropical winter surface pressure patterns. Using a 30‐hPa index of the QBO, we demonstrate that the observed teleconnection with the Arctic Oscillation (AO) is likely to be real, and a teleconnection with the North Atlantic Oscillation (NAO) is probable, but not certain. Simulated QBO‐AO teleconnections are robust, but appear weaker than in observations. Despite this, inconsistency with the observational record cannot be formally demonstrated. To assess the robustness of our results, we use an alternative measure of the QBO, which selects QBO phases with westerly or easterly winds extending over a wider range of altitudes than phases selected by the single‐level index. We find increased strength and significance for both the AO and NAO responses, and better reproduction of the observed surface teleconnection patterns. Further, this QBO metric reveals that the simulated AO response is indeed likely to be weaker than observed. We conclude that the QBO can potentially provide another source of skill for Northern Hemisphere winter prediction, if its surface teleconnections can be accurately simulated. Link to full paper: https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2018JD029368
  6. Bring Back 1962-63

    [Eastern US] Jan. 2019 Pattern & Forecast Disc. #2

    Copied from the Teleconnections thread. It looks like we are nearly there! What to look for in the models I've still very little time to produce a full post, so I'll do a summary. I'm writing this report for several threads on two weather forums (US and UK) with a full spectrum of readers - so I'll use simple terms. There have been some excellent posts on here in recent weeks and this post will pick up on the timing and coupling issues such as those just referred to by @BestW (welcome to this forum). Despite the great advances in our understanding of the teleconnections and how they influence the atmosphere and the broad scale patterns, there are still challenges at certain times in understanding how they interact with each other, constructively or destructively and which ones dominate at particular times. The GSDM (global synoptic dynamic model) pulls this together and gives us a great heads up into what is going on and what we "might" expect and look out for in the coming weeks, months and seasons. It's just as important to understand what can go wrong and why as it is when everything goes according to plan. This winter has been both truly fascinating and (so far) pretty frustrating for the cold and snow brigade. We know that a major SSW (sudden stratospheric warming) and particularly a split SPV (stratospheric polar vortex) usually leads to widespread HLB (high latitude blocking) in the Arctic with a lot of cold displaced towards the middle latitudes. No two SSWs are alike. Occasionally the wind reversals in the strat never down well to the trop (troposphere), to influence the surface patterns. More often they do produce surface impacts but this can be pretty quickly (in just one or two weeks) or after a protracted period. These timing issues are mostly in relation to the "coupling" between the strat and the trop. When they are in harmony, down welling can proceed much more smoothly. Since the 2018 SSW and the final warming in the Spring, the strat and trop have been pretty decoupled. In fact, it is this which has delayed and prevented (so far) a full El Nino from developing despite a number of attempts and this has defied most of the main ENSO forecasts. We have seen short periods of El Nino like conditions but with brief La Nina like setbacks. This SSW started off in late December as a displaced SPV which quickly split in early January. The wind reversals in the middle and lower strat lasted for most of this month. There is a recovery underway up there now (which does not mean that the event is over - far from it) and the reversals are at last down welling through the trop. It looks like full surface impacts will be seen in the high Arctic within a week or so. We still need the trop to be receptive (with other teleconnections acting constructively) and it was back in late December but far less so for much of January but the next cycle of tropical forcing has been underway during the last few days. This is where +ve GLAAM (global atmospheric momentum) anomalies push polewards from the tropics. We saw +ve mountain torque events and the GWO (global wind oscillation) is in a higher orbit in phase 6. GLAAM and the torques are key parts of the GSDM. Another part of this forcing mechanism is shown by the MJO (Madden Julian Oscillation) with areas of tropical convection progressing from west to east. This too is entering key phases in its cycle which are more favourable for HLB. In fact ECM has now joined GEFS (and several other models) with increased amplitude from phase 6 into phase 7 within a few days (indicated on both the VP200 and RMM charts). There are the usual time lags and the benefits from both the GWO and MJO in favourable phases are usually seen some 7 to 10 days later - ie: on this occasion very much in harmony with the Arctic surface impacts. There are still two mores ingredients. One of these is the ENSO state with weak El Nino conditions considered to be most favourable for tropical forcing. A WWB (westerly wind burst) is underway in the western tropical Pacific and progressing steadily eastwards. This will be associated with an upturn in the Nino region temperatures which is just getting underway right now. The final ingredient is FT (frictional torque) which has been stubbornly -ve all month - in fact it was last +ve at the equator and northern tropics in late December. FT has been rising for the last 3 or 4 days and on the Jan 24th chart (always produced 2 days afterward) it was heading towards +ve territory and is probably already there. +ve FT really assists with the tropical forcing (caused by the stresses created by tropical convection and changes in AAM). It should help with the strat/trop coupling down there which may well see this El Nino event finally get over the line with a sustained period of Nino conditions as well as contributing to the overall poleward push of momentum. So, it looks like all this is finally occurring with a much greater degree of harmony. The AO (Arctic oscillation) is already going -ve and should go more strongly -ve next week with HP showing up near the pole. The PNA (Pacific North American oscillation) is also going +ve with the Aleutian LP setting up. The down stream pattern of ridges and blocks then develops in conjunction with the forced extensive HLB from the Arctic. The Canadian PV should weaken and be pushed further south. HP is likely to rise in the Greenland area. Siberian, Arctic and Scandinavian HPs should all be seen at stages and the NAO (North Atlantic oscillation) should at last go -ve. For Europe and the UK an extended period of north easterlies or easterlies are favoured. The current LPs with increasingly polar maritime and Arctic incursions in it should be forced southwards or south eastwards. Given the long SSW event in the strat,, we can expect these surface conditions to dominate for much of February and perhaps well into March too. Eastern CONUS and Canada should see even more extensive and prolonged cold. Just how much snow any of us see will be decided closer to the events but all of us should see a fair amount of it. So, once again, I've been very bullish. I do hope that we do not see another "curve ball" - but this time it does look like our patience will be fully rewarded. Those with model fatigue need to recharge their batteries. We can expect the models to pick up on these imminent changes increasingly during the next few runs. In fact there has already been a shift. UKMO looks to be the most progressive with D6 Arctic blocking (and consistent with their extended outlook). Exciting times ahead. David
  7. It looks like we are nearly there! What to look for in the models I've still very little time to produce a full post, so I'll do a summary. I'm writing this report for several threads on two weather forums (US and UK) with a full spectrum of readers - so I'll use simple terms. There have been some excellent posts on here in recent weeks and this post will pick up on the timing and coupling issues such as those just referred to by @BestW (welcome to this forum). Despite the great advances in our understanding of the teleconnections and how they influence the atmosphere and the broad scale patterns, there are still challenges at certain times in understanding how they interact with each other, constructively or destructively and which ones dominate at particular times. The GSDM (global synoptic dynamic model) pulls this together and gives us a great heads up into what is going on and what we "might" expect and look out for in the coming weeks, months and seasons. It's just as important to understand what can go wrong and why as it is when everything goes according to plan. This winter has been both truly fascinating and (so far) pretty frustrating for the cold and snow brigade. We know that a major SSW (sudden stratospheric warming) and particularly a split SPV (stratospheric polar vortex) usually leads to widespread HLB (high latitude blocking) in the Arctic with a lot of cold displaced towards the middle latitudes. No two SSWs are alike. Occasionally the wind reversals in the strat never down well to the trop (troposphere), to influence the surface patterns. More often they do produce surface impacts but this can be pretty quickly (in just one or two weeks) or after a protracted period. These timing issues are mostly in relation to the "coupling" between the strat and the trop. When they are in harmony, down welling can proceed much more smoothly. Since the 2018 SSW and the final warming in the Spring, the strat and trop have been pretty decoupled. In fact, it is this which has delayed and prevented (so far) a full El Nino from developing despite a number of attempts and this has defied most of the main ENSO forecasts. We have seen short periods of El Nino like conditions but with brief La Nina like setbacks. This SSW started off in late December as a displaced SPV which quickly split in early January. The wind reversals in the middle and lower strat lasted for most of this month. There is a recovery underway up there now (which does not mean that the event is over - far from it) and the reversals are at last down welling through the trop. It looks like full surface impacts will be seen in the high Arctic within a week or so. We still need the trop to be receptive (with other teleconnections acting constructively) and it was back in late December but far less so for much of January but the next cycle of tropical forcing has been underway during the last few days. This is where +ve GLAAM (global atmospheric momentum) anomalies push polewards from the tropics. We saw +ve mountain torque events and the GWO (global wind oscillation) is in a higher orbit in phase 6. GLAAM and the torques are key parts of the GSDM. Another part of this forcing mechanism is shown by the MJO (Madden Julian Oscillation) with areas of tropical convection progressing from west to east. This too is entering key phases in its cycle which are more favourable for HLB. In fact ECM has now joined GEFS (and several other models) with increased amplitude from phase 6 into phase 7 within a few days (indicated on both the VP200 and RMM charts). There are the usual time lags and the benefits from both the GWO and MJO in favourable phases are usually seen some 7 to 10 days later - ie: on this occasion very much in harmony with the Arctic surface impacts. There are still two mores ingredients. One of these is the ENSO state with weak El Nino conditions considered to be most favourable for tropical forcing. A WWB (westerly wind burst) is underway in the western tropical Pacific and progressing steadily eastwards. This will be associated with an upturn in the Nino region temperatures which is just getting underway right now. The final ingredient is FT (frictional torque) which has been stubbornly -ve all month - in fact it was last +ve at the equator and northern tropics in late December. FT has been rising for the last 3 or 4 days and on the Jan 24th chart (always produced 2 days afterward) it was heading towards +ve territory and is probably already there. +ve FT really assists with the tropical forcing (caused by the stresses created by tropical convection and changes in AAM). It should help with the strat/trop coupling down there which may well see this El Nino event finally get over the line with a sustained period of Nino conditions as well as contributing to the overall poleward push of momentum. So, it looks like all this is finally occurring with a much greater degree of harmony. The AO (Arctic oscillation) is already going -ve and should go more strongly -ve next week with HP showing up near the pole. The PNA (Pacific North American oscillation) is also going +ve with the Aleutian LP setting up. The down stream pattern of ridges and blocks then develops in conjunction with the forced extensive HLB from the Arctic. The Canadian PV should weaken and be pushed further south. HP is likely to rise in the Greenland area. Siberian, Arctic and Scandinavian HPs should all be seen at stages and the NAO (North Atlantic oscillation) should at last go -ve. For Europe and the UK an extended period of north easterlies or easterlies are favoured. The current LPs with increasingly polar maritime and Arctic incursions in it should be forced southwards or south eastwards. Given the long SSW event in the strat,, we can expect these surface conditions to dominate for much of February and perhaps well into March too. Eastern CONUS and Canada should see even more extensive and prolonged cold. Just how much snow any of us see will be decided closer to the events but all of us should see a fair amount of it. So, once again, I've been very bullish. I do hope that we do not see another "curve ball" - but this time it does look like our patience will be fully rewarded. Those with model fatigue need to recharge their batteries. We can expect the models to pick up on these imminent changes increasingly during the next few runs. In fact there has already been a shift. UKMO looks to be the most progressive with D6 Arctic blocking (and consistent with their extended outlook). Exciting times ahead. David
  8. No time for a full post but today's charts (just out look much better): Total AAM and Earth AAM rising, relative GLAAM tendency anomaly is sky rocketing to its highest level all winter (and for a long time prior to that), GLMT doing the same and EAMT rising again. Then this: There was an error over the last 2-3 days with this GWO chart stuck but it has now adjusted with the update to Jan 20th - now doing what we hoped for - much higher orbit in P5. MJO on GEFS & ECM now predicted to go through P6 and into P7 at moderate amp before decaying. PNA looking better - now mixed with 50% of members going +ve. AO still -ve but only NAO rather disappointing - although even that is less +ve. Encouraging signs going forward but I'll watch it all from a distance while I finish off my annual accounts. David CAUTIONARY NOTE: I should add that after discussions in our PM thread, we still need frictional torque to play ball in the tropics and this has remained stubbornly -ve. So some encouraging news but still a potential problem to keep an eye on going into February. D @earthlight - John, here's the GWO chart source that you requested; http://gsdmsolutions.com/~gsdm/clim/gcm/ David
  9. At last we have what we've been predicting - a poleward surge in +ve AAM. Another important piece in the jigsaw for Arctic blocking: The relative GLAAM tendency anomaly has spiked upwards and looks set to reach its highest level of the winter. Global MT is surging upwards and both NAMT and EAMT are strongly +ve too. The GWO has already looped back into phase 5 and is set to go into a much higher orbit through phases 5, 6 and 7. This is the strong tropical forcing that we've been saying is needed to assist the down welling in the stratosphere. So far, I believe that the models have just begun to sniff out the SSW surface impacts. They usually struggle to pick up on the tropical forcing. So we go from a pretty destructive phase into a really constructive one. In the mid term (say day 10 onwards but perhaps sooner and remember that these charts have a 2 day output time lag) this should hugely assist with the HLB patterns. I would expect the models to start picking up on this over the next few days but with various blocking outcomes and solutions. A CAUTIONARY NOTE: We still need to monitor how the jet stream phasing in the Pacific behaves and this has impacts on the US storm system(s) and a knock on down stream in the Atlantic. This may or not not be favourable in the short term but given the prolonged SSW event, the strength of the MT spikes and poleward momentum the opportunity is likely to persist for many days (or weeks). Continued exciting model watching for the rest of this month and beyond. No more time this week. David
  10. Bring Back 1962-63

    [Eastern US] Jan. 2019 Pattern & Forecast Discussion

    Hi Zac, this is a truly outstanding post which is an early nomination for "post of the year". Although based on the teleconnections (as it should be) you've presented it in such a clear way, that many readers will be able to understand it. The forces which are producing this major pattern change across the middle and higher latitudes are exceptional. The models are still coming to terms with this SSW and it's impacts. Assuming that the downward propagation through the troposphere continues to the surface, this should provide even greater displacement of the Arctic surface cold to you guys and in Eurasia too (which should include the UK). Even without a full wind reversal down welling (full surface impacts seem inevitable now), the strat is starting to imprint on the trop patterns and widespread significant cold looks likely to dominate for quite a few weeks. IMHO the main building blocks are very much in place and it's the finer detail which will evolve during the next week or so which the models are still toying with. ECM (and the UKMO) do seem to be getting there now. When the other teleconnections (AAM, the torques, the MJO and renewed modest Nino-like forcing come into play again around the turn of the month and into early Feb, they only need to produce modest impacts to really constructively assist with a continuation of the SSW dominated set up. What an absolutely fascinating period for all weather enthusiasts. David
  11. Bring Back 1962-63

    [Eastern US] Jan. 2019 Pattern & Forecast Discussion

    A FEW COMMENTS ON THE GREAT LOOKING POTENTIAL FOR CONUS AND UK/EURO COLD Hi everyone, I rarely come onto this thread as I normally post on the Teleconnections thread and occasionally on the Stratosphere thread. This will not be one of my long in depth reports with loads of charts (I have little time for that now anyway) but I wanted to make a few comments. One thing that we know is that many weather forums are far busier during the winter and the majority of members are looking for cold and snowy conditions to prevail. Most of us who analyse the background signals and the teleconnections are also snow lovers but we try to tell it as it is and endeavour not to allow our emotions to overly influence the points that we are making. I'm from the UK, where we often miss out on snow in our marginal climate adjacent to the Atlantic and a major continent. Much of central and eastern Europe is currently seeing it's heaviest snowfalls for 30 years. Some spots at only moderate altitude have seen well over 1 m (3 feet) of the white stuff this week with 2 m to even 3 m in the mountains of southern Germany and Austria. Almost as much again is forecast for the next few days. Malcolm @Blessed Weather (another "33" UK member is currently on a skiing holiday in Bavaria (on the German/Austrian border) and he's snowed in there - far too much for skiing but he's having a wonderful time anyway and he'll post some pics on this forum in due course. Here's one pic that he took yesterday during a brief break in the snowfalls - just to get us all in the mood: Back in the UK, like you guys we're still waiting for the real cold to arrive. We need even more patience than you do across the pond and we have to be used to many disappointments and near misses. On the UK forum that I'm also a member of, the emotions runs even higher than they do on "33". I must say that I'm so pleasantly surprised that there is generally a far higher level of respect shown on here compared to back in the UK. I do, however, feel that Tom @Isotherm (amongst several others) has seen a few rather unfair comments. He has been trying to point out what can go wrong, although he remains very upbeat about the rest of the winter. I agree with him and feel that both the eastern/central CONUS (and eastern Canada) and western Europe (including the UK) are "likely" to see prolonged periods of very cold conditions starting to dominate from late January and through much of February (precise timing subject to some variation). We have been studying the stratosphere and the troposphere and looking at all the key teleconnections throughout the year especially during the fall and the run in to winter. The stratosphere looked like delivering an SSW this winter and these signs grew stronger from late November with possible triggering of a major event from late December into early January. As we know this actually happened with a displaced SPV (stratospheric polar vortex) between Xmas and the New Year and just a few days later with a fully split SPV - in fact a really impressive event indeed. No two SSWs are alike. Sometimes the "wind reversals" never reach the surface, sometimes they are delayed and sometimes they propagate down very quickly. Much depends on other factors and the key teleconnections. This is not the thread to go into any detail but we need to consider the ENSO state (a very weak and still struggling to move into full El Nino conditions - may not get there until the spring now but probably still enough "nino" like conditions overall to be favourable), angular momentum and the torques (were playing ball and likely will again in early-mid Feb) , the MJO (was in favourable phases for high latitude blocking and looks set to quickly return to those phases in early Feb too albeit at weaker amplitude), all this impacts on the critical amount of tropical forcing, the QBO (recently changed to west based - on its own not so favourable) and the solar cycle (getting close to a roughly 11 year minimum = very favourable). The consensus in our Teleconnections PM group was that we looked set for colder than normal patterns for large parts of this winter even without a major SSW. Indeed Tom's winter forecast picked up on this. What we have seen for a while was a disconnect between the strat and the trop and some of the favourable tropical forcing "was" initially being somewhat cancelled out by the strat warming (in the build up to the SSW). This is called acting "destructively". Things, however, now look like they are really falling into place and we should see some of the key teleconnections and the SSW impacts acting much more "constructively" later this month and even more so in February. With all this going on, we know that the models really struggle with both sniffing out these major broad scale pattern changes and the timing of any impacts. Our strat specialists are seeing signs of the "wind reversal" down welling through the troposphere. It looks like surface impacts will be seen in the high Arctic (close to the pole) within the next 7 to 10 days (again precise timing cannot be certain and there might be several more days delay but there is increasing confidence of this now which is starting to show up in some of the model op runs and certainly a good number of ensemble members are showing this evolution. The next question is exactly where will the impacts be felt first, how will they develop, how will they spread, how cold will it get and how long will it last? With split SPVs, surface impacts are usually much more widespread. The Arctic cold is pushed out towards the middle latitudes, Much depends on the strat/trop imprint and the tropical forcing processes that I outlined but this is looking like a really strong SSW impact which will be the dominant factor for some weeks. Sometimes North Am sees the impacts first but more often with splits Eurasia see them first. The Feb/Mar 2018 SSW impacted Siberia and then the blocking patterns spread westwards through Europe and across the pond reaching you guys about 10 days later. Then there was a secondary warming with a similar response. You ended up with repeated cold periods in March and into April. The models are starting to indicate more of an initial impact on our side of the pond with you guys seeing the main changes some days later. In the interim, both you and western Europe are likely to see some colder shots anyway. I'm not going to discuss your winter storm prospects or ours and how much snow any of us will see. Let's just say that there is some wonderful "potential" for the next 6 weeks (or even longer). Of course there's a small chance that things can still go pear shaped (slightly more likely for me in the far south west of England but less likely for the eastern UK, much of Europe and of course eastern CONUS) but I would be very surprised if we do not see at least some decent cold spells with snow pretty likely. We are in the middle of a truly fascinating transition with so much to look forward to. Let's all be patient and watch the evolution from now on and particularly during the latter part of January onwards. David
  12. MUCH MORE ON AAM I'm really busy for the next few days and then have my annual business accounts to complete - so no time to review particular AAM papers now but here's the list of titles to papers and presentations already in the portal under the AAM heading (you can click on any title): Atmospheric Angular Momentum (AAM): A gentle stroll through EP (Eliassen & Palm) flux theory An Essay on the General Circulation of the Earth's Atmosphere (1947) Angular momentum in the global atmospheric circulation A Synoptic–Dynamic Model of Subseasonal Atmospheric Variability Atmospheric Dynamics Feedback: Concept, Simulations, and Climate Implications Atmospheric forcing mechanisms of polar motion Atmospheric torques and Earth’s rotation: what drove the millisecond-level length-of-day response to the 2015–2016 El Niño? Axial Angular Momentum: Vertical Fluxes and Response to Torques Centennial Trend and Decadal-to-Interdecadal Variability of Atmospheric Angular Momentum in CMIP3 and CMIP5 Simulations Dynamic coupling of the stratosphere with the troposphere and sudden stratospheric warmings Gravity wave refraction by three-dimensionally varying winds and the global transport of angular momentum Isentropic Pressure and Mountain Torques Latitude–Height Structure of the Atmospheric Angular Momentum Cycle Associated with the Madden–Julian Oscillation Mountains, the Global Frictional Torque, and the Circulation over the Pacific–North American Region Mountain torques and atmospheric oscillations Mountain Torques and Northern Hemisphere Low-Frequency Variability. Part I: Hemispheric Aspects Mountain Torques and Northern Hemisphere Low-Frequency Variability.Part II: Regional Aspects Planetary‐scale wave activity as a source of varying tropospheric response to stratospheric sudden warming events: A case study Regional Sources of Mountain Torque Variability and High-Frequency Fluctuations in Atmospheric Angular Momentum Relationship between Tropical Pacific SST and global atmospheric angular momentum in coupled models Relation between variations in the intensity of the zonal circulation of the atmosphere and the displacements of the semi-permanent centers of action Response of the Zonal Mean Atmospheric Circulation to El Niño versus Global Warming Stochastic and oscillatory forcing of global atmospheric angular momentum Studies of atmospheric angular momentum The Angular Momentum Budget of the Transformed Eulerian Mean Equations The atmospheric angular momentum cycle during the tropical Madden-Julian Oscillation The Dynamics of Intraseasonal Atmospheric Angular Momentum Oscillations The Effects of Mountains on the General Circulation of the Atmosphere as Identified by Numerical Experiments The intraseasonal atmospheric angular momentum associated with MJO convective initiations The layer of frictional influence in wind and ocean currents [1935] The remote effect of the Tibetan Plateau on downstream flow in early summer The Role of Mountains in the Angular Momentum Balance of the Atmosphere The tropical Madden-Julian oscillation and the global wind oscillation Topographic Instability: Tests Tornado Frequency in the United States Related to Global Relative Angular Momentum Torques and the Related Meridional and Vertical Fluxes of Axial Angular Momentum Uncertainty analysis of atmospheric friction torque on the solid Earth Unusual Behavior in Atmospheric Angular Momentum during the 1965 and 1972 El Niños What is the GSDM and how does it help with subseasonal weather forecasts? (A YouTube Presentation) Where is ENSO stress balanced? Some of these papers are entirely about AAM while others are make considerable reference to it amongst other related teleconnections. What we deliberately designed the Research Portal for was to enable visitors to skim through papers quickly by providing links to the abstract. Once anyone reads the abstract they can decide if they wish to look at the full paper (or view the presentation) itself with a direct link provided under the abstract. When I read papers, I initially look at the introduction and then the conclusions. If I feel that I want to learn more and especially if I wish to review a paper in one of my posts, then I delve into it much more deeply. I've learnt a lot more by reviewing papers and presentations as I have to get my head around the main points in order to comment on them meaningfully (hopefully ). I could never understand the maths and all the equations but focus on the text. There are always some bits that one can understand even in the more complex papers. One cannot learn much about AAM without understanding the GWO (global wind oscillation) which is referenced in many posts on this thread. There is a specific GWO heading in the portal index. In fact, check out all these headings (shown in alphabetical order): Brewer-Dobson Circulation East Asian Mountain Torque Frictional Torque Global Wind oscillation Global Synoptic Dynamic Model (more on this below) Mountain Torque North American Mountain Torque Planetary Waves Rossby Waves (similar to above) That's just a handful of topics directly related to AAM - there are many others. Here's a link to the full comprehensive index: INDEX TO PAPERS Unlike many meteorological topics there are no really simple guides available to AAM as it's such an extensive and pretty complex topic (it would be good if somebody wrote one!). A great place to start is with a brilliant YouTube presentation by Ed Berry all about the GSDM (global synoptic dynamic model) which I posted a review and summary on last May. Here's the link to that post https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=87746 . That reminds me, I've been working on an index to this thread which appears at the top of each page. I've got up to September but still have a lot of work to do in the coming months to bring it right up-to-date. There are some good earlier posts on here to explore. This index heading contains posts with significant references to the GSDM including my review on May 24th: Edward K Berry (Ed) and Dr Klaus Weickmann (devised the GSDM and the GWO and pioneers in the application of AAM and the torques) March 26th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83549 @Snowy Hibbo May 24th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=87746 @Bring Back 1962-63 July 1st 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=88574 @Bring Back 1962-63 July 29th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=89707 @Isotherm July 29th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=89714 @Bring Back 1962-63 Here's a list (below) of the posts with a focus on AAM. I highly recommend those from March and April when Zac @Snowy Hibbo, Tams @Tamara, Malcolm @Blessed Weather and myself were getting this thread off the ground with some posts introducing the subject and generally aimed at learners. I produced a long post entitled: UNDERSTANDING THE BASICS ABOUT ATMOSPHERIC ANGULAR MOMENTUM FROM A LEARNER’S PERSPECTIVE. I wrote it for early learners and go though how and why I wanted to understand this vitally important subject. Here's the link: https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83979 It does have several small errors in it but it does provide a comprehensive beginner's guide to the processes involved. It's the March 30th entry in the list below. Do check out the posts from the others too who have greater AAM knowledge than I do (especially back then): Atmospheric Angular Momentum (AAM) and Global Atmospheric Angular Momentum (GLAAM) March 26th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83549 @Snowy Hibbo March 26th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83567 @Bring Back 1962-63 March 26th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83568 @Tamara March 27th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83666 @Blessed Weather March 29th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83745 @Snowy Hibbo March 29th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83753 @Tamara March 30th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=83979 @Bring Back 1962-63 April 17th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=86401 @Blessed Weather April 22nd 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=86675 @Bring Back 1962-63 May 24th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=87746 @Bring Back 1962-63 June 2nd 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=87925 @Snowy Hibbo June 3rd 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=87946 @Bring Back 1962-63 July 1st 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=88574 @Bring Back 1962-63 July 29th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=89707 @Isotherm July 29th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=89714 @Bring Back 1962-63 August 31st 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=91074 @Snowy Hibbo September 15th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=95282 @Snowy Hibbo September 15th 2018 https://www.33andrain.com/topic/868-teleconnections-a-more-technical-discussion/?do=findComment&comment=95305 @Tamara Overall, this thread and the Research Portal already contain a vast amount of teleconnection information with plenty on AAM and the torques - all available on this great forum. I have nearly 1,000 more papers saved in my store ready to upload during the course of this year. The numbers grow more quickly than I can find the time to write the portal entries! Malcolm, Zac and myself are the portal administrators but if anyone would like to help us build it up we would really appreciate the extra help. Please PM any of us about this. David
  13. An outstanding post Zac with a really clear and comprehensive explanation of the AAM processes which are difficult to understand and something that I'm still in the middle learning stages of myself after 2 years of trying to get my head around it. Geoff @33andrain - please can you make Zac's post a "recommended post" and leave it there at the top of the Teleconnections thread page for a few weeks. Not only will readers learn from this but it will help to refer to it when any of us post AAM and torque charts while the SSW impacts unfold during the next 2 to 8 weeks. David
  14. LOOKING FOR SSW SURFACE IMPACTS NEAR THE POLE IN THE MODEL OUTPUT - COMPARISONS TO EARLIER EVENTS - PART 2: 2013 I'm writing this post for two weather forums (US and UK) but most of it is relevant to both N America and UK/Europe. I will be mainly drawing on charts produced by Meteoceil and these + archived charts from the NCEP reanalysis show the Northern Hemisphere from the UK perspective. Abbreviations used in this post: SSW - Sudden Stratospheric Warming SPV - Stratospheric Polar Vortex TPV - Troposheric Polar Vortex HLB - High Latitude Blocking QBO - Quasi Biennial Oscillation MJO - Madden-Julian Oscillation COD - Circle Of Death GSDM - Global Synoptic Dynamic Model GWO - Global Wind oscillation GLAAM - Global Atmospheric Angular Momentum FT - Frictional Torque MT - Mountain Torque EAMT - East Asian Mountain Torque NAMT - North American Mountain Torque What I want to examine are the surface pressure patterns and charts in relation to previous SSWs and to show what to look out for in the current output. My focus will be for signs of the reversal propagating down to the surface in the high Arctic and close to the North Pole. I will look at charts around the time each main SSW event started, at the time of the specific types developed (ie: the displacement and/or the split), the time that surface impacts were beginning to show up and one or more later chart(s) to see how blocking patterns fell into place. I am dividing this post into at least 3 parts over several days to cover separate SSW events. In part 1, I looked at the current set up and then the February 2018 SSW (direct link to that post: https://www.33andrain.com/topic/750-stratospheric-discussion-and-forecasting/?do=findComment&comment=115201. In this post (part 2) I'll focus on the 2013 SSW and in part 3, the 2009 SSW. Later on, I may move on to several earlier events - time permitting. I note a request from @Weathergeek wrt to the 1984/5 SSW. While there is no GLAAM, torque or MJO data available for back then, I can show the reanalysis charts for that "split" SPV event - I'll do a separate short post on it (next week) once I've completed this (and perhaps part 3) over this weekend. 2012/2013 SSW: SSW started in late December 2012; Rapid warming occurred between December 28th, 2012 and January 10th, 2013; 10hPa wind reversal on January 6th 2013; Type - Displaced SPV January 6th, 2013 and Split from January 8th; Ended February 8th, 2013; longest SSW on record (38 to 42 days depending on which analysis you read) in the modern "satellite" era (since 1979). MJO - phases 4 and 5 at increasing amp at the time of SSW, then on to phases 6 and 7 at moderate to high amp later in January; ENSO - neutral with perhaps slightly La Nina like tendency (see table below); wQBO (descending); solar cycle - closer to maximum (reached in April 2014 but the weakest since 1902) . The 2012/13 SSW was an unusual and fascinating SSW with both displaced and split SPVs. This is probably only the third (possibly fourth) time that this has occurred since at least 1978 (in the modern satellite era). Depending on which reports one reads the previous years were 1985/86 (some contention on the displacement but ended up as a split event), 1987/88 (split, then displaced with a further warming and another split two months later) and 2001/02 (displaced and perhaps a split later on). the 2012/13 event with combined wave 1 and wave 2 attacks leading to the displaced then split SPV events was the longest since at least 1978 lasting 38 to 42 days. With such a long event, the impacts lasted at intervals right through to mid April with repeated bouts of HLB and cold spilling out of the Arctic. You can see that ENSO was slightly on the -ve side of neutral throughout the period but not strong enough to be defined as a La Nina episode. This table (up to 2013) shows the phase state of the MJO at the time of the "start" of major SSW events. Although the MJO can have an influence at that stage, we also need to see to what extent it might have assisted during the impact period. From the archives, we can see that the MJO was actually still in phase 4 at the time of the initial SSW event and then progressed through the phases from 5 to 8 at moderate to quite high amp. ignore the green "forecast" period. I pick it up from mid February. Although the amp was much lower in phase 1 it never entered the COD and then managed another complete orbit at low to moderate amp. it reached phases 6, 7, 8 and 1 at slower reducing amp between Feb 25th and March 21st. The briefly slightly stronger amp in phases 6 and 7 (allowing for the time lagged impacts) was probably at least partly assisting renewed blocking through mid to late match (see model charts further below). It's a difficult exercise obtaining GLAAM and torque data from the archives. NOAA closed their map room in 2015/6 for this when Dr Klauis Weickmann and Ed Berry (who developed the GSDM and GWO) left. Ed berry (whom I'm in touch with by email) says that it's a time consuming (and therefore costly) exercise to reprocess the raw data (which is still available) to reproduce the archive charts again. I've been through countless papers, presentations and archived forum posts to find some earlier charts and have been building up a store of some of the key data. Unfortunately many charts no longer show in early posts and many charts that do show up were copied across with the (copy image address option" and these charts "auto update. I found a 2009 post with a current GLAAM chart showing! I save all of these type of charts to a file which freezes the image and date. if anyone has access to a good range of archived AAM and torque charts (and also GWD - gravity wave drag charts for my 2019 focus research project) from 2005 to 2016, please let me know. I (and the specialists in this field) would really appreciate having a permanent and complete record of all archived charts. Unfortunately, I could not find any torque charts for January to April 2013 but I do have enough useful data in my store to piece the GLAAM and torque position together. This MT chart is up to Dec 24th 2012 and shows a huge spike in global MT (black line) to an extremely +ve position and still rising at the end. NAMT (blue) was +ve but falling back and EAMT (red) is rising strongly and looking set to go into a strongly +ve phase. Given the 10 to 14 days (or so) time lag, it would look that once again, EAMT played a significant role in helping to trigger the SSW. As usual and fully consistent with the latest research (and the papers that I've read) the deeper red blobs in the upper part of the chart are between 35N and 50N and show us that the strongest MT was around the Tibetan Plateau and particularly the Mongolian Mountains. The area which generates the greatest uplift in the world with vertically propagating planetary waves and (gravity waves too through gravity wave drag). Remember that we should consider that this is still "theory" but I've been gathering more and more evidence to support that theory. We can see that relative AAM spiked just after mid January and that "may" well have led to another spike in the torques later in January and into early February. This table shows GLAAM averaged out for each calendar month from 1958 to 2014. December 2012 was +ve, January 2013 was neutral (as we can see the mid month spike was cancelled out but -ve momentum earlier and later), then Febraury to April 2013 all averaged out broadly +ve but not particularly strongly. That's confirmed by the chart above. That longer period of +ve GLAAM would have been strongly supportive of the repeated HLB patterns and may well have been the main factor in keeping the troposphere in its generally -ve AO and -ve NAO state for many weeks beyond the end of the SSW itself. Now on to what some of you have been waiting for - the archived model charts. I will not comment on these other than to say that you'll see repeated periods of HLB with some lulls. Here's the link so that you can go through the whole period: http://www.meteociel.fr/modeles/archives/archives.php?day=1&month=1&hour=0&year=2013&map=4&region=&mode=2&type=ncep Finally a word of caution wrt to the current event. No two SSWs are the same and even similar type of events can have very different impacts. There remains uncertainty on the timing issues but it seems that we can all take comfort in a long SSW event which may, like 2013 (which has both similarities but many difference too) see several GLAAM, torque and MJO cycles creating repeated opportunities. I do not know how patient we'll need to be but perhaps you can see why the models always struggle with these episodes - there is such a complex interaction of the strat, the trop. and all the teleconnections. I remain very confident of some prolonged cold or very cold weather but no one right now can nail down the timing of the impacts. GLMT and EAMT are still +ve but less so and their time lagged benefits (+ the MJO still in phase 7 and on to 8 for a while longer) should last through to around Jan 20th or longer. Part 3 on the 2009 SSW (which has rather more similarities to the current event but also some significant differences) will follow later on during the week - I'm unlikely to have more time before then. David
  15. LOOKING FOR SSW SURFACE IMPACTS NEAR THE POLE IN THE MODEL OUTPUT - COMPARISONS TO EARLIER EVENTS - PART 1: 2019 AND 2018 I'm writing this post for two weather forums (US and UK) but most of it is relevant to both N America and UK/Europe. I will be mainly drawing on charts produced by Meteoceil and these + archived charts from the NCEP reanalysis show the Northern Hemisphere from the UK perspective. Abbreviations used in this post: SSW - Sudden Stratospheric Warming SPV - Stratospheric Polar Vortex TPV - Troposheric Polar Vortex HLB - High Latitude Blocking QBO - Quasi Biennial Oscillation MJO - Madden-Julian Oscillation COD - Circle Of Death SOI - Southern Oscillation Index GWO - Global Wind oscillation GLAAM - Global Atmospheric Angular Momentum FT - Frictional Torque MT - Mountain Torque EAMT - East Asian Mountain Torque What I want to examine are the surface pressure patterns and charts in relation to previous SSWs and to show what to look out for in the current output. My focus will be for signs of the reversal propagating down to the surface in the high Arctic and close to the North Pole. I will look at charts around the time each main SSW event started, at the time of the specific types developed (ie: the displacement and/or the split), the time that surface impacts were beginning to show up and one or more later chart(s) to see how blocking patterns fell into place. I will divide this post into at least 3 parts over several days to cover separate SSW events. In part 1, I will look briefly at the current set up and then focus on the February 2018 SSW. In part 2 I'll focus on the 2013 SSW and in part 3, the 2009 SSW. Later on, I may move on to several earlier events - time permitting. Firstly, we need to see the dates, type and length of each event. I repeat this table for reference: This only goes up to 2010. Malcolm @Blessed Weather has kindly helped me obtain similar data for the 2013 event and there is plenty of data available on the Feb 2018 event. If nothing else, these posts will confirm that every SSW is different in many ways. The type of warming with the displaced and/or split vortex events as we know are highly important with the latter "usually" leading to more extensive HLB. The propagation and down welling of the wind reversal to the surface is often far from straight forward and precise timings are extremely difficult to nail down even within the D5 to D7 period. 2019 SSW: SSW started in late December 2018 (precise date to be confirmed). Type - Split, circa January 3rd, 2019. MJO - phases 5 and 6 with 7 and 8 predicted at moderate amp; ENSO - weak El Nino developing (there is a minor blip right now but do not get hung up on the SOI and on some of the S Hem ENSO impacts); wQBO (descending); solar - near minimum. I'll start with the current "ongoing" event which I'll call the "2019 SSW" to avoid confusing it with the earlier 2018 event although the warming in the upper layers started in mid/late December 2018 with repeated attacks on the SPV. GEFS and ECM are much more closely aligned now compared to the last couple of weeks but there is still some uncertainty over how fast the progression will be. In the second half of January we would normally expect this to favour HLB. As this SSW looks like being a long (or even very long) event it would not be too bad if the MJO misses out on its 1 to 4 phases and re-emerges in phase 5/6 again for a repeat performance (perhaps at higher amp) during February to give us a second bite of the cherry. I appreciate that on our side of the pond phases 7 and 8 (and 1) are better for blocking patterns while in N America phases 8 and 1 (and 2) are better. The GWO is now strengthening again and progressing through phase 5 and looking set for phase 6 (if it's not there already with the 2 day chart time lag). The relative GLAAM tendency anomaly has been rising again as is total GLAAM. That's encouraging for +ve tropical forcing but there has been a timing issue. Ideally, we would want to see the SSW surface impacts more or less coincide and it is not completely certain that GLAAM will be maintained in an elevated for more than the next 10 days or so. It is, however, pretty likely that the GWO will perform in a similar way to the MJO and it has been on a repeat cycle since early November. So we might see both January and February impacts. FT (not shown) remains +ve. A reminder of the GWO phase chart. Then we have further good news. Global MT (black line) is +ve and just recently, rising further. This should prevent EAMT (red line) from falling back too far and it'll likely remain +ve for even longer. The strongest signal is at 30N to 40N (the red blobs in the upper part of the chart) centred around the Tibetan Plateau (see my early posts for greater details on this). The +ve torques should assist in keeping GLAAM +ve for an extended period with perhaps only a short weaker or -ve blip. Now to relate this to the models. I prepared this post based on today's 0z and 6z output and I know that the 12z will be out by the time I've finished. As there has been considerable run to run variability this does not really matter as output is likely to remain volatile for at least several more days and possibly rather longer than that. What I noted however, was some remarkable "consistency" on the day 5 output (something not seen at all on previous runs with considerable disagreement): I'll just show the GEFS 6z "mean" for today. The moderate amplification that we've seen so far has been related to the +ve GLAAM, torques and the MJO at decent amp through phase 6. This has produced some quite stationary or slow moving ridges and troughs and the recent cold plunge into Europe which looks set to be repeated during next week. I'll leave it to other posters to comment on their shorter term "home" patterns be it UK, Europe or N America. I'm really focusing on the high Arctic. There are just hints of HP building closer to the North Pole. Now the January 9th chart. HP is building right over the pole. and the TPV is looking set to split just to the south. This is the mean chart but every GEFS ensemble member has HP over the pole at this time (see below), plus the control run + the GFS operational run. Here's the panel : EDIT: I had saved the 6z but the gif updated to the 12z which still has all the members with HP building around the pole. Moreover so do "all" the other main models - GFS (parallel), ECM, GEM, NAVGEM, JMA and ICON. As you'll see when I cover the 2018 and earlier SSWs, these are important early signs. This coupled with the latest news on the stratosphere suggesting that the reversal is now down welling through the troposphere with several commentators suggesting that this may only be 3 or 4 days away. Now, please do not take this as definite - things can still go wrong or at least we may have further delays. The fact that all the models agree on around day 5 for the first signs of polar impacts is encouraging. Rather than pushing things back, if we can move things forward then we'll get the best combination of GLAAM and the torques with the tropical forcing with stronger HLB much more likely and assisting better strat-trop coupling. The full story is still in its early stages. Will the existing amplified pattern link up to HLB? Will there be a transition of a few days with a flatter pattern? Where will the blocking set up? How severe will the cold be and how long will it last? "If" there is a further delay, things still look good into February. So the 2019 SSW still teases us but I remain very optimistic of widespread cold weather going forward with some earlier rather than delayed impacts. 2018 SSW: SSW started during February 2018. Type - Split, circa February 12th, 2018. MJO - phases 3, 4, 5 and 6 at increasing amp and entering phase 7 at around record high amp (see below); ENSO - moderate La Nina (but with a weaker phase in January) eQBO; solar - weak and falling. Note that the MJO was in high amp phase up to the time of the initial triggering of the SSW on February 12th, then continued at weaker amp through to phase 8 (ignore the forecast "green" bit as I'm looking at what actually occurred). The time lagged impacts on HLB fitted in very nicely. This chart from the archives (see below) shows that the MJO continued through phase 1 at increasing amp then onto phase 2 (good for N America which saw the SSW impacts a week to 10 days after the UK and Europe) and briefly into phase 3 before passing through the COD and back out to phase 7 towards the end of March. Here's a link to the archived NOAA weekly reports going back to 2006 and these contain the phase charts and a lot more. http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/ARCHIVE/PDF/ Unlike the current event, GLAAM had been strongly -ve through much of January 2018 and rose strongly at decent amp through phase 4 and 5 into early February and at moderate amp through phases 6 , 7 and into 8 by February 10th. So pretty strong and with +ve torques in the build up to the SSW. The spike in global MT and EAMT in early February and with that 10 to 14 day time lag almost certainly helped to trigger the SSW on February 12th. The next spike may well have assisted the secondary warming. I covered this in more detail in my last post. Now the models. I'm using the excellent NCEP reanalysis charts from the archives. You can trace the whole of the 2018 SSW and much more on this link: http://www.meteociel.fr/modeles/archives/archives.php?day=12&month=2&hour=0&year=2018&map=4&region=&mode=2&type=ncep The SPV split on February 12th and models were generally showing pretty mundane output (seems familiar?). We had some polar maritime air in the UK and central/eastern CONUS and Canada had a "standard" (not SSW related) Arctic outbreak. Just one week later and the models were starting to sniff out something going on and there were signs of the pattern reversal impacting with the build of HP at the pole but only very modest amplification of the Azores HP. Strong HP over central and northern Asia and building across from Alaska. This post is already getting very long but for those of you who want to see how variable the model "forecast" output was a few days before, run through the archived "forecast" charts - here's a link: http://www.meteociel.fr/modeles/gfse_cartes.phpjour=7&mois=2&annee=2018&heure=12&archive=1&mode=0&ech=6&runpara=0&carte=1 You can play around with all the output and reset the date ranges etc. A further week on and it's getting very interesting. Arctic HP extending to Iceland and Scandinavia. The "Beast from the East" was just awakening over Europe and the UK. Note that the TPV was still over northern Canada but it was shortly to be on its journey across to Siberia. Just 4 days later and the TPV had migrated across to Siberia. A true Greenland HP had developed. The surface flow reversal was now pushing on right through CONUS. The beast is at its most intense over western Europe and the UK. Three more days later and the reversed flow at the surface shot through Europe, the UK, across the Atlantic, Newfoundland and through to central CONUS. After weakening somewhat, the SSW (with its secondary warming impacts) is having another go. The "Mini beast" (or beast 2) hits Europe and the UK Canada and central CONUS saw the most severe impacts during much of April 2018. Although the current and the February/March 2018 SSWs were both "split" SPV events you can see that the build up had some similarities but also many differences too. One can see how quickly the model output changed and how dramatic these events can be. I hope that we will see something very special from this event. Watch out for those Arctic profiles and the HP building there. Next up in part 2 (tomorrow) I'll look at the 2013 SSW which had a displaced and a split SSW with separate impacts over a prolonged period. David
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